So sex is only for procreation?
Are you going to tell God what He can and cannot do when someone directly disobeys? In those times it was a tooth for a tooth.......stonning those who committed certain sexual sins....etc.,
Of course not......sex is reserved for marriage under the terms outlined in the N.T., sometimes sex is a release of one's lust to stop he/she from sinninig in immorality. One must remember you are quoting from an antiquated law reserved expressly for those under another covenant. God no longer speaks directly to man, nor does the law from which you quoted still exist.
Why design something in the human body and then say........don't use it or I will kill you?

Again......it was not the crime of spilling his seed.......it was the disobedience, as explained when you read from the entire text and subjective content.
God designed sex for both reproduction and relase of lust....i.e, sexual release. God specifically designed the union of marriage to be the primary method for the release of sexual desire that is designed into both men and women, "Nevertheless, because of sexual immorality, let each man have his own wife......." -- 1 Cor. 7:2
Sex outside marriage is sinful under the N.T. of Christ Jesus (Hebrews 13:4)....its considered fornication.
A wife is to submit to the husand in sexual relations and the husband to the wife. (1 Cor. 7:3-4).
God no longer speaks to anyone by the prophets or personally, He...... in these last days speaks through the words of His Son Christ Jesus (Hebrews 1:1-2) The old laws were nailed to the cross of the Christ (Col. 2:14)
Even the prophets of old declared there would come a time when the Law of Moses would be replaced by a New Law written on the hearts of those who believed (Jer. 31:31-34)